Materials that produce color change upon stimulation with energy (e.g., light or heat) may have possible applications in imaging. For example, such materials may be found in thermal printing papers and instant imaging films. Generally, the materials and compositions known so far may require a multifilm structure and further processing to produce an image (e.g., instant camera films). And in the case of facsimile and thermal head media, high energy input of greater than 1–5 J/cm2 is needed to achieve good images. The compositions in multifilm media may require control of diffusion of color-forming chemistry and further processing, and are in separate phases and layers. Many thermal and facsimile paper coatings consist of coatings prepared by applying fine dispersions of more than two components. The components mix and react upon application of energy, resulting in a colored material. For the necessary mixing, the particles may need to contact across three or more phases or layers and merge into a new phase. Because of these multiple phases and layers, high energy is required to perform this process. For example, a relatively powerful carbon dioxide laser with an energy density of 3 J/cm2 at times of much greater than 100 μs may be needed to produce a mark. In some instances, this high energy application may cause damage to the imaging substrate.
In many situations, it may be desirable to produce a visible mark more efficiently using either a less intense, less powerful, and/or shorter energy application. Therefore, there is a need for fast marking coatings, possibly composed of fewer than three phases and in single layer. One method may be to provide a binder, a dye, a color developer, and an antenna, wherein the dye changes color when reacted with the color developer, wherein one of the dye and the color developer is soluble in the binder at ambient conditions, wherein the antenna and the binder soluble compound are dissolved in the binder; and the other of the dye and the color developer compound are substantially uniformly distributed in the binder. In such systems, if the antenna is not substantially thermally and light stable, the ability to mark may be lost or diminished, i.e., due to absorption of ambient energy (e.g., sunlight, artificial light, and/or ambient heat). The antenna may lose its ability to absorb energy and deliver it for formation of an image. For example, even antennae which have previously been considered stable (i.e., with an extinction coefficient greater than 100,000, or less than 20% loss in absorption, after exposure to light or heat stress) may be highly susceptible to ambient energy and may show diminished light marking ability after exposure to ambient energy.
In addition, the formed image may fade if it has not been developed with sufficient energy. For example, many markings may fade after exposure to 40° C./80% humidity after three days. This fading may be due to the inability of the antenna to deliver sufficient energy to the dye, especially due to effect of exposure to light or heat. Heretofore, it may be desirable to produce a system which solves one or more of the foregoing problems.